The synthetic substrate for palmitoyl-protein thioesterase 1 (PPT1) is 4-methylumbelliferyl-6-thioplamitoyl-beta-glucoside. The fibroblasts are homogenized and combined with protein and a substrate and incubated. The reaction is stopped with a glycine buffer. The fluorescence of the 4-methylumbelliferone product is read using a fluorescence plate reader and activity is calculated based on amount of product formed during the 1-hour incubation period.(Van Diggelen OP, Keulemans JLM, Winchester B, et al: A rapid fluorogenic palmitoyl-protein thioesterase assay: Pre and postnatal diagnosis of INCL. Mol Genet Metab 1999;66:240-244)

The synthetic substrate tripeptidyl peptidase 1 (TPP1) is Ala-Ala-Phe-7-amino-4-methylcoumarin. The fibroblasts are homogenized and combined with protein and a substrate and incubated. The reaction is stopped with a glycine buffer. The fluorescence of the 7-amino-4-methylcoumarin product is read using a fluorescence plate reader and activity is calculated based on amount of product formed during the 1-hour incubation period.(Sohar I, Lin L, Lobel P: Enzyme-based diagnosis of classical late infantile neuronal ceroid lipofuscinosis: comparison of tripeptidyl peptidase I and pepstatin-insensitive protease assays. Clin Chem 2000;46:1005-1008)